Lights went out across the world tonight to mark Earth Hour, the biggest-ever mass event to highlight public ­concern over climate change. Global landmarks from Australia to China, Egypt, France, Britain and America went dark for an hour at 8.30pm local time.

The event began on the Chat­ham Islands in the Pacific, followed by Fiji, where drummers entertained the crowds and ­diners ate by candlelight.

In Australia, where the first Earth Hour was held two years ago, people attended candlelit speed-dating events and outdoor concerts as the hour of darkness swept across the country. Lights on Sydney Harbour Bridge and the Opera House were dimmed, while Twitter users posted regular updates. "Melbourne hasn't been this dark in a century," one reported.

At the Vatican, the dome of St Peter's Basilica went dark, as did the pyramids at Giza, the Eiffel Tower in Paris and New York's Empire State Building. Across the UK, hundreds of schools and businesses switched off or dimmed lighting, while landmarks including the Houses of Parliament, Nelson's Column and Edinburgh Castle went dark. Coca-Cola switched off its famous advertising screen at Piccadilly Circus for only the third time since the second world war.

At Scott Base in Antarctica, the winter team from New Zealand reduced their lighting to minimum safety lamps and switched off all appliances and computers. In Beijing, officials turned out lights at the Olympic Bird's Nest Stadium and Water Cube venues. In Shanghai, government buildings were dimmed.

WWF, the environment campaign group which was co-ord­inating the global event, expected millions of people to turn out lights in the hope of sending a message to world leaders that their voters want urgent action to save the planet. Andy Riley of WWF Australia, who co-ordinated the global event, said: "We need massive change; one hour in terms of change is not that much. We want people to think about what they can do to lower their carbon footprint, and ideally take that beyond the hour." The idea for Earth Hour grew out of a similar WWF Australia campaign in 2007. For the global version, the group chose 2009 because of the negotiations scheduled in Copenhagen later this year to set climate targets for when the Kyoto protocol runs out in 2012.

Colin Butfield, head of campaigns at WWF UK, said: "Earth Hour is a simple way to make sure that our leaders really understand that people are looking to them to do what is right and that the time for action is now."